I am a programmer...

There is absolutely no need for an EXE to be registered in the registry. It is easy to create a program that is stand-alone, Can be run or not, Can be deleted without affecting any other part of the computer or living traces and residue.

Your skeptisism is misplaced here.

The fact that every program you have installed has registered itself is due to your choice of program - I have used (and created) a great many programs that do not register themselves [it is actually easier to create a non-registering program than one that registers itself].

Mark